The interaction of B and T lymphocytes continues to be a major area for investigation. We propose to examine a variety of B lymphocyte responses to antigen and determine the influence of T lymphocytes on these responses; included will be proliferation, IgM to IgG receptor switch, and maturation to antibody production. In addition, the effect of T lymphocytes on affinity maturation of B lymphocytes will be determined, both from the viewpoint of the preferential proliferation of high affinity B lymphocytes and the affinity-dependent T cell suppression of B lymphocyte differentiation to IgG antibody production. As a corollary to this study, we will attempt to determine whether helper and suppressor functions are manifestions of the same or different populations of T lymphocytes, or whether the T lymphocyte effect is predominantly a function of the B lymphocyte. An additional area of investigation will be to determine whether the T-independent antibody response in guinea pigs is different from that of mice, as preliminary evidence has indicated. Finally, a study of clonal dominance will be made to determine the cellular mechanism of restriction.